If the spring of a jack-in-the-box is compressed a distance of 8 cm from its relaxed length and then released what is the speed of the toy head when the spring returns to its natural length? assume the mass of the toy head is 50 g the spring constant is 80 n/m, the toy head news only in the vertical direction. also disregard the mass of the spring. (hint: remember that there are two forms of potential energy in the problem.)

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.